Particles, bonding and bulk properties
Введено| English | Значение |
|---|---|
| ionic bond/aɪˈɒnɪk bɒnd/ | ионная связь |
| delocalized electron/dɪˈlɒkəlaɪzd ɪˈlektrɒn/ | делокализованный электрон |
What would explain this observation?
- A salt crystal conducts when dissolved but not when solid. The ions exist in both states; their ability to move changes.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Ionic bonding 离子键 is electrostatic attraction between oppositely charged ions. A covalent bond involves shared electrons. Metallic bonding involves attraction between positive metal ions and delocalized electrons 离域电子.
- ionic bond: Attraction between oppositely charged ions; delocalized electron: An electron not confined to one atom or bond.
Why does molten sodium chloride conduct?
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Sodium chloride is ionic; melting frees the ions from the lattice so they can move and carry charge. The solid does not conduct because its ions are fixed, and there are no neutral molecules or free atoms becoming electrons.
Match each technical term to its precise meaning.
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Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- To explain a bulk property, name the structure, particles, forces and mobile charge carriers. Simple molecular substances can have strong covalent bonds inside molecules but weak attractions between molecules.
- Compare substances using evidence such as melting point, conductivity when solid and molten, and solubility. One property rarely proves a structure; use a pattern of evidence.
Which two habits make the investigation or model in this case more defensible?
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Stating the conditions and assumptions lets others repeat the work exactly, and recording the supporting evidence lets them check the conclusion. Hiding disagreeing results removes the evidence that could challenge a wrong conclusion, and one measurement can never establish a wider claim.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: an element has atomic number 12 and mass number 24. Protons = 12; neutrons = mass number - atomic number = 24 - 12 = 12. A 2+ ion has electrons = 12 - 2 = 10. Charge changes electron count, not the nucleus.
An atom has atomic number 17 and mass number 35. Find its number of neutrons. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
An atom has atomic number 17 and mass number 35. Find its number of neutrons.
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The result is 18 . Known: atomic number 17, mass number 35. Neutrons = mass number - atomic number = 35 - 17 = 18. The atom has 17 protons and 18 neutrons; changing the electron count would make an ion, not change the nucleus.
Check the conclusion and its limits
- Melting a simple molecular substance usually overcomes intermolecular attractions; it does not require breaking all covalent bonds within each molecule.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
All covalent substances have low melting points. This claim is false: Giant covalent substances such as diamond and silicon dioxide have very high melting points because covalent bonds must be broken throughout the structure. Low melting points belong to simple molecular substances, where only intermolecular attractions are overcome.
Particles, bonding and bulk properties: To explain a bulk property, name the structure, particles, forces and mobile charge carriers. Simple molecular substances can have strong covalent bonds inside molecules but weak attractions between molecules.
All covalent substances have low melting points.
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Giant covalent substances such as diamond and silicon dioxide have very high melting points because covalent bonds must be broken throughout the structure. Low melting points belong to simple molecular substances, where only intermolecular attractions are overcome.
Attraction between oppositely charged ions: write the technical term.
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ionic bond means Attraction between oppositely charged ions.